FRP Engineering is proud to announce our all new line of extreme performance Race Gas and E85 Pistons for Audi - AAN and 3B inline five cylinder engines. They are the result of a considerable engineering partnership with Wiseco Piston and have been proven in the FRP Land Speed Record holding S4 sedan.

These are the first "flow and compression optimized" racing pistons for these engines utilizing true 3D dome milling and Aero Humps that interface with the intake valves during overlap to enhance cylinder filling and increase scavenging of burned exhaust gasses.

These pistons have 6cc positive dome volume and are intended to be used in ported combustion chambers where bore matching and flow relieving around the valves produce chamber volumes of 48 to 51 cc's. These pistons produce a 10.1 to 1 CR in engines with 86.4 mm strokes and a 50 cc chamber volume and a standard .062 MLS gasket. With a 92.8 stroke they produce 10.65 to 1 with the same accompanying specs.

These compression ratios are required when the builder / tuner are trying to take maximum advantage of high octane, slow burning race gas or with E85 to E98 fuels and their lower caloric heat content and high latent heat cooling properties.

Stock chamber volume is 45 to 46 cc's. These pistons have a positive deck height that requires that thechamber be opened to the bore size. When doing this mod it is really smart to just go ahead and un - shroud around the valves as this is a substantial benefit to low and mid lift flow. The MLS head gasket must also be bored out to fit the bore size. This is simple and Hank has a fixture at his shop for opening the gasket to bore size. Stock size valves will work fine and will just have additional clearance with the piston and chamber walls.

Okay so opening the chambers to the block bore size (how far vertical do you need to go?) and unshrouding the valves alone should put it in the ideal chamber size range? Y'all do the plexiglass and water trick or is there a better way?

Pistons have a bevel at the top but the stock chamber overhangs the bore considerably on the sides and a little behind the exhaust valves. This varies slightly from head to head. Best practice, if you want to do the work yourself, is to use a head gasket of the accompanying bore size and machinists dye around the chambers. Place the gasket precisely over the chambers and the dowel holes. Tape it into place and use a fine pointed scribe to mark the bore diameter onto the head surface. Port the chamber to bore size at least .200 deep into the chamber. I prefer a blend to the chamber roof to avoid creating crevice volume. As stated earlier the head gasket must be opened up to bore size plus .2 mm to avoid the piston crown scuffing on the gasket.

Yes I use a graduated burette and "the plexi glass thing" like everyone else. I use mineral spirits as apposed to water. Rubbing alcohol works well too.